// Original license //
// ---------------- //

/*
Copyright 2011 Google Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// All other modifications and improvements //
// ---------------------------------------- //

/*
 * Modern Copy, (C) 2015 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package s3

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"sort"
	"strings"
	"time"

	"crypto/hmac"
	"crypto/sha1"
	"crypto/tls"
	"encoding/base64"
)

func (a *s3Client) loadKeys(cert string, key string) (*TLSConfig, error) {
	certBlock, err := ioutil.ReadFile(cert)
	if err != nil {
		return nil, err
	}
	keyBlock, err := ioutil.ReadFile(key)
	if err != nil {
		return nil, err
	}
	t := &TLSConfig{}
	t.CertPEMBlock = certBlock
	t.KeyPEMBlock = keyBlock
	return t, nil
}

func (a *s3Client) getTLSTransport() (*http.Transport, error) {
	if a.CertPEM == "" || a.KeyPEM == "" {
		return &http.Transport{
			Dial: (&net.Dialer{
				Timeout:   30 * time.Second,
				KeepAlive: 30 * time.Second,
			}).Dial,
			TLSHandshakeTimeout: 10 * time.Second,
		}, nil
	}

	tlsconfig, err := a.loadKeys(a.CertPEM, a.KeyPEM)
	if err != nil {
		return nil, err
	}
	var cert tls.Certificate
	cert, err = tls.X509KeyPair(tlsconfig.CertPEMBlock, tlsconfig.KeyPEMBlock)
	if err != nil {
		return nil, err
	}

	// Setup HTTPS client
	tlsConfig := &tls.Config{
		Certificates:       []tls.Certificate{cert},
		InsecureSkipVerify: true,
	}

	tlsConfig.BuildNameToCertificate()
	transport := &http.Transport{TLSClientConfig: tlsConfig}
	return transport, nil
}

func (a *s3Client) signRequest(req *http.Request, host string) {
	if date := req.Header.Get("Date"); date == "" {
		req.Header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
	}
	hm := hmac.New(sha1.New, []byte(a.SecretAccessKey))
	ss := a.stringToSign(req, host)
	//fmt.Printf("String to sign: %q (%x)\n", ss, ss)
	io.WriteString(hm, ss)

	authHeader := new(bytes.Buffer)
	fmt.Fprintf(authHeader, "AWS %s:", a.AccessKeyID)
	encoder := base64.NewEncoder(base64.StdEncoding, authHeader)
	encoder.Write(hm.Sum(nil))
	encoder.Close()
	req.Header.Set("Authorization", authHeader.String())
}

// From the Amazon docs:
//
// StringToSign = HTTP-Verb + "\n" +
// 	 Content-MD5 + "\n" +
//	 Content-Type + "\n" +
//	 Date + "\n" +
//	 CanonicalizedAmzHeaders +
//	 CanonicalizedResource;
func (a *s3Client) stringToSign(req *http.Request, host string) string {
	buf := new(bytes.Buffer)
	buf.WriteString(req.Method)
	buf.WriteByte('\n')
	buf.WriteString(req.Header.Get("Content-MD5"))
	buf.WriteByte('\n')
	buf.WriteString(req.Header.Get("Content-Type"))
	buf.WriteByte('\n')
	if req.Header.Get("x-amz-date") == "" {
		buf.WriteString(req.Header.Get("Date"))
	}
	buf.WriteByte('\n')
	a.writeCanonicalizedAmzHeaders(buf, req)
	a.writeCanonicalizedResource(buf, req, host)
	return buf.String()
}

func hasPrefixCaseInsensitive(s, pfx string) bool {
	if len(pfx) > len(s) {
		return false
	}
	shead := s[:len(pfx)]
	if shead == pfx {
		return true
	}
	shead = strings.ToLower(shead)
	return shead == pfx || shead == strings.ToLower(pfx)
}

func (a *s3Client) writeCanonicalizedAmzHeaders(buf *bytes.Buffer, req *http.Request) {
	var amzHeaders []string
	vals := make(map[string][]string)
	for k, vv := range req.Header {
		if hasPrefixCaseInsensitive(k, "x-amz-") {
			lk := strings.ToLower(k)
			amzHeaders = append(amzHeaders, lk)
			vals[lk] = vv
		}
	}
	sort.Strings(amzHeaders)
	for _, k := range amzHeaders {
		buf.WriteString(k)
		buf.WriteByte(':')
		for idx, v := range vals[k] {
			if idx > 0 {
				buf.WriteByte(',')
			}
			if strings.Contains(v, "\n") {
				// TODO: "Unfold" long headers that
				// span multiple lines (as allowed by
				// RFC 2616, section 4.2) by replacing
				// the folding white-space (including
				// new-line) by a single space.
				buf.WriteString(v)
			} else {
				buf.WriteString(v)
			}
		}
		buf.WriteByte('\n')
	}
}

// Must be sorted:
var subResList = []string{
	"acl",
	"location",
	"logging",
	"notification",
	"partNumber",
	"policy",
	"requestPayment",
	"torrent",
	"uploadId",
	"uploads",
	"versionId",
	"versioning",
	"versions",
	"response-content-type",
	"response-content-language",
	"response-expires",
	"response-cache-control",
	"response-content-disposition",
	"response-content-encoding",
	"website",
}

// From the Amazon docs:
//
// CanonicalizedResource = [ "/" + Bucket ] +
// 	  <HTTP-Request-URI, from the protocol name up to the query string> +
// 	  [ sub-resource, if present. For example "?acl", "?location", "?logging", or "?torrent"];
func (a *s3Client) writeCanonicalizedResource(buf *bytes.Buffer, req *http.Request, host string) {
	bucket := a.bucketFromHost(req, host)
	if bucket != "" {
		buf.WriteByte('/')
		buf.WriteString(bucket)
	}
	buf.WriteString(req.URL.Path)
	sort.Strings(subResList)
	if req.URL.RawQuery != "" {
		n := 0
		vals, _ := url.ParseQuery(req.URL.RawQuery)
		for _, subres := range subResList {
			if vv, ok := vals[subres]; ok && len(vv) > 0 {
				n++
				if n == 1 {
					buf.WriteByte('?')
				} else {
					buf.WriteByte('&')
				}
				buf.WriteString(subres)
				if len(vv[0]) > 0 {
					buf.WriteByte('=')
					buf.WriteString(url.QueryEscape(vv[0]))
				}
			}
		}
	}
}

// hasDotSuffix reports whether s ends with "." + suffix.
func hasDotSuffix(s string, suffix string) bool {
	return len(s) >= len(suffix)+1 && strings.HasSuffix(s, suffix) && s[len(s)-len(suffix)-1] == '.'
}

func (a *s3Client) bucketFromHost(req *http.Request, host string) string {
	reqHost := req.Host
	if reqHost == "" {
		host = req.URL.Host
	}

	if reqHost == strings.TrimPrefix(host, "http://") {
		return ""
	}

	if reqHost == strings.TrimPrefix(host, "https://") {
		return ""
	}

	if reqHostSuffix := strings.TrimPrefix(host, "https://"); hasDotSuffix(reqHost, reqHostSuffix) {
		return reqHost[:len(reqHost)-len(reqHostSuffix)-1]
	}

	reqHost, _, _ = net.SplitHostPort(reqHost)
	return reqHost
}